Clarify some confusing casts involving |size_t|.

Change-Id: I7af2c87fe6e7513aa2603d5e845a4db87ab14fcc
Reviewed-on: https://boringssl-review.googlesource.com/7101
Reviewed-by: David Benjamin <davidben@google.com>

crypto/cipher/cipher_test.cc

@@ -138,7 +138,7 @@ static bool TestOperation(FileTest *t,
                                iv.size(), 0)) {
         return false;
       }
-    } else if (iv.size() != (size_t)EVP_CIPHER_CTX_iv_length(ctx.get())) {
+    } else if (iv.size() != EVP_CIPHER_CTX_iv_length(ctx.get())) {
       t->PrintLine("Bad IV length.");
       return false;
     }

crypto/cipher/e_aes.c

@@ -384,7 +384,7 @@ static int aes_ecb_cipher(EVP_CIPHER_CTX *ctx, uint8_t *out, const uint8_t *in,
 
 static int aes_ctr_cipher(EVP_CIPHER_CTX *ctx, uint8_t *out, const uint8_t *in,
                           size_t len) {
-  unsigned int num = ctx->num;
+  unsigned num = (unsigned)ctx->num;
   EVP_AES_KEY *dat = (EVP_AES_KEY *)ctx->cipher_data;
 
   if (dat->stream.ctr) {
@@ -394,7 +394,7 @@ static int aes_ctr_cipher(EVP_CIPHER_CTX *ctx, uint8_t *out, const uint8_t *in,
     CRYPTO_ctr128_encrypt(in, out, len, &dat->ks, ctx->iv, ctx->buf, &num,
                           dat->block);
   }
-  ctx->num = (size_t)num;
+  ctx->num = (int)num;
   return 1;
 }
 

crypto/rsa/padding.c

@@ -95,7 +95,7 @@ int RSA_padding_add_PKCS1_type_1(uint8_t *to, unsigned to_len,
   memset(p, 0xff, j);
   p += j;
   *(p++) = 0;
-  memcpy(p, from, (unsigned int)from_len);
+  memcpy(p, from, from_len);
   return 1;
 }
 
@@ -189,7 +189,7 @@ int RSA_padding_add_PKCS1_type_2(uint8_t *to, unsigned to_len,
 
   *(p++) = 0;
 
-  memcpy(p, from, (unsigned int)from_len);
+  memcpy(p, from, from_len);
   return 1;
 }
 
@@ -271,7 +271,7 @@ int RSA_padding_add_none(uint8_t *to, unsigned to_len, const uint8_t *from,
     return 0;
   }
 
-  memcpy(to, from, (unsigned int)from_len);
+  memcpy(to, from, from_len);
   return 1;
 }